[U-Boot] R: Re: Strange arm9 behaviour reading long(s) not aligned to 4 bytes boundary
I have something like this on a 32 bit little endian arm9 board (SAM9
L9260):
char buffer[] = { 0, 1, 2, 3, 4, 5, 6, 7 };
long A = * (
(long*)
buffer ); long B = * ( (long*) (buffer + 2) );
printf("A: %
08x B: %08x", A,
B);
I would expect that A = 0x03020100 and B =
0x05040302
instead I get the right value for A but B is 0x01000302 or
something like this but anyway not
what I expect. Is there something
wrong on the board? It seems that only 4
bytes aligned long are read
correctly.
ARM9 does not support unaligned load/store. Yours is apparently
configured in the round-and-rotate mode. e
Then my code is simply wrong, that is, not allowed? If I have to port code from a PPC (that handles unaligned accesses) to an ARM9 it is painful operation..., isn't it?
Bye, Antonio.
Dear Antonio,
In message 10799135.81041232909531093.JavaMail.defaultUser@defaultHost you wrote:
Then my code is simply wrong, that
Basicly, yes.
is, not allowed? If I have to port code from a PPC (that handles unaligned accesses)
...then you should fix the PPC code as well.
to an ARM9 it is painful operation..., isn't it?
This has nothing to do with ARM.
Porting broken code is always a pain, though.
Best regards,
Wolfgang Denk
"dibacco@libero.it" dibacco@libero.it writes:
I have something like this on a 32 bit little endian arm9 board (SAM9L9260):
char buffer[] = { 0, 1, 2, 3, 4, 5, 6, 7 };
long A = * ( (long*) buffer ); long B = * ( (long*) (buffer + 2) );
printf("A: %08x B: %08x", A, B);
I would expect that A = 0x03020100 and B = 0x05040302 instead I get the right value for A but B is 0x01000302 or something like this but anyway not what I expect. Is there something wrong on the board? It seems that only 4 bytes aligned long are read correctly.
ARM9 does not support unaligned load/store. Yours is apparently
configured in the round-and-rotate mode.
Then my code is simply wrong, that is, not allowed? If I have to port code from a PPC (that handles unaligned accesses) to an ARM9 it is painful operation..., isn't it?
If your code relies on unaligned memory accesses, then yes, making it run on an ARM9 might not be much fun. I would suggest you set the processor to trap on unaligned accesses (the manual will tell you how). That should make it easier to find them all.
participants (3)
-
dibacco＠libero.it -
Måns Rullgård -
Wolfgang Denk